Field of the Invention
The invention relates to a method and a device for determining a valid lane marking, in which at least a first lane marking and a second lane marking different from the first lane marking are detected and one of these detected markings is selected as the relevant lane marking.
Description of Related Art Including Information Disclosed Under 37 CFR 1.97 and 1.98
In the prior art, camera-based driver assistance systems are known which comprise one or more mono or stereo cameras for observation and analysis of an area in front of the vehicle in the direction of travel. For capturing pictures for use in driver assistance systems both black-and-white camera systems and color camera systems are known which capture pictures of a detection area in front of the vehicle in the direction of travel and generate image data corresponding to these pictures. The image data are processed by least one processing unit, the pictures being analyzed and in particular images of objects in the pictures being detected and the objects being classified. In this connection, the detection and the classification are usually restricted to those objects that are relevant for the respective driver assistance system. Besides object recognition, the processing unit in particular performs object tracking, traffic sign recognition of objects classified as traffic signs, lane recognition and/or recognition of vehicles driving ahead and/or of oncoming vehicles. For lane recognition, usually the lane is detected on which the vehicle itself currently moves. Neighboring lanes might be detected as well. In this connection, it is possible that for example a lane change assistant provides an information or a warning to the driver when, for example, the currently used lane is left without an activation of the direction indicator. For detection of the currently used lane, the respective driver assistance system uses the markings that are applied to the lane for lane marking. However, in particular in the case of several overlapping lane markings it is difficult to detect the currently valid lane marking and to then use it for the respective driver assistance system which provides a driver assistance function on the basis of the lane markings. Such overlapping lane markings for example occur in areas of roadworks where at least for some part of the lane a so-called temporary lane marking at roadworks is applied in addition to the original permanent lane marking for the duration of the road construction work.
In Germany, for example, the permanent lane marking is applied to the lane in the color white and the temporary lane marking is applied in the color yellow. Thus, in a roadworks area as well as in an entry area and an exit area of a roadworks area differing lane markings are applied which the human eye usually distinguishes via their difference in color. The colors of temporary and permanent lane markings vary from country to country. Methods for distinguishing between temporary and permanent markings that are exclusively based on color information are thus dependent on an information as to in which country the vehicle moves. Further, although the use of the temporary marking is standardized, these standards are not always observed so that, for example, also in Germany, a yellow marking may be the relevant marking on the left side and a white marking may be the relevant marking on the right side at roadworks. Thus, even when using color cameras, the problem may occur that in bad light conditions, in particular when it rains, the distinction between the lane markings on the basis of their color is not possible with sufficient certainty. Further, by means of black-and-white cameras the colors differences may only be detected by differences in brightness of the different colors in the picture. In this way, a distinction between valid and non-valid markings is not possible with sufficient certainty. But the use of black-and-white cameras for capturing pictures for use in driver assistance systems has the advantage that CMOS image sensors, as used in particular in black-and-white cameras, allow for a high image resolution and a high gray level resolution of, for example, 4096 gray levels. At present, such a gray level or brightness resolution cannot be achieved with comparable color sensors. Also the further processing of the image data is considerably reduced in the case of black-and-white images compared to the further processing of the image data of color images so that the use of black-and-white cameras in driver assistance systems is advantageous.
From the document EP 1 653 310 A2, a method for the directional control of a road-bound vehicle using a camera mounted at a defined position on the vehicle is known. With the aid of the camera, a permanent lane marking is detected. Here, marking patterns are detected after entering a danger zone or an area of roadworks, and a control signal for the transverse directional control of the vehicle is determined.
From the document DE 103 112 40 A1, a method and a device for the directional control of a vehicle is known, in which a distinction is made between temporary and permanent markings on the lane. Whenever temporary markings are detected, these are preferably used for the directional control of the vehicle.
From the document DE 10 2004 003 848 A1, a method for recognizing marked danger zones and/or roadworks in the area of lanes is known. These methods use spatial separation images of a detection area of a sensor for electromagnetic radiation, for example a laser scanner, mounted on a vehicle. In the spatial separation images, distinguishing features for a danger zone and/or roadworks are looked for.